George Steinbrenner is on his way to becoming one of the most powerful figures in sports, industry executives say.

In addition to his plans to sell a piece of the Yankees to the public, Steinbrenner is eyeing a possible bid for the Jets and some other entertainment assets as the cornerstone of a regional sports network.

Steinbrenner’s moves could also set up the Boss as a major rival to Cablevision’s Charles Dolan.

The transformation of the Yankees from the No. 1 sports brand into a budding media conglomerate is expected to begin in a matter of days with the completion of the merger of the Yankees and the Nets.

Those working on the deal were rushing yesterday to complete the YankeeNets merger.

It is expected to be announced Monday, although it could be sooner, according to persons familiar with the situation.

The teams’ financial advisers valued the Yanks at $600 million and the Nets at $150 million, those persons said. Steinbrenner will continue to head up the Yankees operation while Nets co-Chairman and principal owner Lewis Katz will continue to run the Nets.

The new company will have little immediate impact on fans.

Down the line, however, it could affect what cable channel airs Yankee games, how much fans pay for their cable service, where the team plays its home games and how much taxpayers may end up paying for a new stadium.

The deal also gives both teams a lot more leverage – not to mention the access to more cash – in their attempt to gain a new stadium and arena.

Of course, a stock offering would have an instant effect on fans. It could be an instant sellout, the best sports IPO ever, and put $1 billion into the pockets of team Steinbrenner.

YankeeNets spokesman Howard Rubenstein would not comment on possible deals down the line but did say “there was no hitch” in the seven month-long talks.

“The deal is very much on track and the partners are quite enthusiastic,” he said.

Dean Bonham, the Denver-based sports industry consultant who helped set up the sale of the NBA’s Denver Nuggets and the NHL’s Avalanche, said Steinbrenner’s inter-sport merger is the first of its kind but just the beginning of how sports empires will be built in the next millennium.

“Building a sports conglomerate from the ground up is different from how it is usually done, which is by adding a sports team to a media empire,” Bonham said.

“If YankeeNets follows through on all their plans it could be the first sports stock offering that makes sense for investors,” Bonham noted. Previous sports stock offerings – Boston Celtics, Cleveland Indians and Florida Panthers – have been financial disasters.

The Yanks’ 12-year, $486-million deal with Cablevision has one year left to run. The Nets deal with Dolan runs through the 2000-2001 season. Re-upping with Cablevision could bring YankeeNets $75 million a year in fees.

By forming their own RSN, YankeeNets will be giving away those fees in the early years as it invests in the system while hoping to bring in even greater sums through its equity control of the RSN.

“All teams are looking for ways to gain equity position in a network,” said Robert Gutkowski, the former president of MSG. “You have to take a long-term approach to maximize the brands.”